Understanding height and area calculations is necessary for proper administration of the building code. These tables are the basis of how big and tall a building can be. The tables are found in chapter 5 of the International Building Code (IBC).
Some definitions to consider (found in section 502 of the IBC):
Area, Building. The are included within surrounding exterior walls (or exterior walls and fire walls) exclusive of vent shafts and courts. Areas of the building not provided with surrounding walls shall be including in the building area if such areas are included within the horizontal projection of the roof or floor above.
Height, Building. The vertical distance from the grade plan to the average height of the highest roof surface.
Height, Story. The vertical distance from top to top of two successive finished floor surfaces; and for the topmost story, from the top of the floor finish to the top of the ceiling joists or, where there is not a ceiling, to the top of the roof rafters.
Mezzanine. An intermediate level or levels between the floor and ceiling of any story and in accordance with section 505.
The basics of height and area are found in the IBC, Table 503. The table requires that the building is classified based on the use group and the type of construction. If you had a restaurant/bar (A2 Occupancy) made out of unprotected wood frame (VB Construction) the maximum area of the building would be 5,500 square feet and 1 story in height.
A similar example would be what is the permissible area of a 10 story business use group building made out of Type IB construction? When referring to table 503, the table states UL and 11-stories. The UL is highlighted in a footnote on the bottom of the table and stands for unlimited area (not underwriters laboratory). Take a look at a building for an H-1 use group made of VB construction. The table indicates NP. In this table, NP stands for “Not Permitted.”
These is the basics of the height and area provisions. Now with any good code text there are exceptions to this rule. We are going to cover these in future articles. I encourage you to look through the sections on allowed increases to the table for things like open perimeter and the installation of an approved automatic sprinkler system